Organic Substances 61 



Methods for saccharides 



I. SUBSTANCES OTHER THAN NUCLEIC ACIDS (GLYCOGEN, 

 MUCIN, GLYCOPROTEIDS, ETC.) 



Fixation and embedding.— While for mucinoid substances 

 almost any fixation will do, the correct fixative for glycogen 

 has been the subject of numerous publications,^^' ^^~^^ and 

 there is still no consensus. Most textbooks on microtechnique 

 recommend alcohol or alcoholic mixtures on the principle 

 that glycogen is insoluble in them while it is soluble in most 

 aqueous fixatives. Theoretically, as applied to pure glycogen, 

 this is a perfectly valid consideration; however, in tissues 

 where glycogen is embedded in a complex mixture of pro- 

 teins and lipids the situation is different. Any good protein 

 precipitant will coat the glycogen particles with a protein 

 membrane which is impermeable to the large molecules of 

 glycogen, thus keeping them in situ. Lison^^ quotes the stud- 

 ies of Pasteels and Leonard, who state that one of the best 

 fixatives is Bouin's fluid. Lillie,^^ on the other hand, finds that 

 Bouin's fluid is an unsuitable fixative for glycogen. The writer 

 agrees with the French workers on the excellence of Bouin's 

 fluid and with Lillie on the poor results obtained with fix- 

 atives containing mercury salts. In summary, it may be said 

 that any good histological fixative, with the exception of sub- 

 limate-containing mixtures, can be used. The best are those 

 which act fast and produce considerable hardening of the 

 tissues ( Bouin's fluid, formalin-alcohol with or without acetic 

 acid, etc. ) . However, the morphology of glycogen wfll vary 

 somewhat with different methods of fixation. In general, alco- 

 holic or acid-containing fixatives cause the aggregation of 

 glycogen into fairly coarse droplets, while simple formalin 

 or formalin-bichromate mixtures reveal a more unfform, fine- 



31. Bensley, C. M.: Stain TechnoL, 14:47, 1939; Deane, H. W., Nesbett, 

 F. B., and Hastings, A. B.: Proc. Soc. Exper. Biol. & Med., 63:401, 1946. 



32. Lillie, R. D.: Bull. Intemat. A. M. Mus., 27:23, 1947; Vallance- 

 Owen, J.: J. Path. & Bact., 60:325, 1948. 



